Biting my tongue on this has been hard. I’ve been beta testing RubyMotion
since earlier this year. It’s pretty slick. This Ars Technica article
by Ryan Paul is a stellar description of it’s history, how it works, and the
caveats.

Yes, this isn’t an official Apple product. Laurent created the open source
MacRuby while at Apple, but struck out on his own to try and actually make a
business around this tool. That’s why you have to purchase a license to use it.
I consider this a feature, not a bug. Laurent and his company, HipByte, are
committing to keep this tool up to date in the face of the rapidly changing iOS
ecosystem. That’s worth paying for.